I've yet to meet a person that isn't blown away by how much better my headphones or iems sound compared to their earbuds/laptop speakers. However, I do have to admit that several just don't really care that much. And some of the ones that do care, can't afford it or justify the cost.

Your comparison doesn't make much sense and I honestly don't even know where to begin explaining exactly how different they are. From design to production process, to shipping differences and market size. Lifespan is wildly different as well. Headphones can last you 20+ years whereas a smartphone will need to be replaced after 3 or 4.

speakers and amplifiers, technologies that existed for decades

This is why I buy used audio gear. The basic guts of the stuff hasn't changed much in the past several decades.

I bought a nice used head unit and speakers 10 years ago. They're 30+ years old now and still work perfectly well.

I’m not sure you read the comment fully, they suggested headphones, not speakers. Just a quiet room is enough for that. Speakers are more expensive because they have to move a lot of air in a room. I’m no expert, but I think it’s the mere physics of doing so accurately that keeps it above 200. A technology can be more or less solved without becoming sub 200.

Anyway, what’s the price range you’re looking for? I’m sure someone can recommend headphones for any range if you’re interested in those.

And that's already a whole lot of money for next to no value for 99% of the people.

I strongly believe those people should not be thinking about audiophile gear. Thankfully, audiophile companies don’t really advertise. The claims most of those companies make are targeted towards people who are into audio, and often feature lots of solid snake oil that 99% of people would not understand. Companies that do advertise heavily tend to emphasize vague things like “deep, rich bass to accurate mids and crisp, clean highs” instead.

And I'm also very very certain that most of the higher end stuff (and I'm counting everything over 200€) is esoteric. You can't hear a difference in quality. Maybe a difference, but not objectively better or worse.

What makes you “very very certain”? There are some quantifiable quality differences, like accurate positioning of sounds or perceived distance from the listener. It may not be necessarily worth the price, but I’m not seeing how you’re “very very certain” everything above 200 is esoteric and that it’s impossible to discern quality.

Problem is, where exactly is the line? It's almost impossible to tell whether this one speaker is garbage with a markup or actually high quality.

Audiophile communities never suggest blind buying because even a high quality product may not have the sound signature you like. It’s similar to how a Rolls Royce, a high quality vehicle, may be too slow and comfortable for someone who would prefer a cheaper Corvette. Those in cities likely have multiple dealers who would be happy to have you come in and sample the stuff, or Best Buy. Pick something you like, regardless of price tag or recommendation. Those not in cities can get on lists of free samples that are then sent to the next listener, or buy and return from stores. Headphones.com has a 365 day return policy intended for this, though there is a restocking fee. Amazon is an unethical company and you can return large dollar quantities without fees before being blacklisted.

Speakers are harder to test if you do not have audio stores or Best Buy. I would still suggest listening when next in a city if possible. I can’t think of anything for those in areas without Best Buy and never enter one, but there might still be something.